• There is a fibromuscular diaphragm in the LA with an opening.
  • The common pulmonary vein fails to get incorporated into the left atrium.
  • The upper compartment is the dilated common pulmonary vein.
  • The lower compartment is the true left atrium.
  • Produces PVH which progresses to pulmonary edema and PAH.
  • Surgery is always needed.